1. Field of the Invention
The present invention relates to ultrasonic scanners and, in particular, to an ultrasonic scanning transducer for examining a specimen and a drive circuit to move the scanning element.
2. Description of the Prior Art
Ultrasonic transducers and scanning techniques are being used to examine specimens to determine various characteristics thereof. Physicians and technicians are using ultrasonic transducers to find abnormalities in human organs and to examine human fetuses in their mothers' uteri. Also, ultrasonic scanners are being used to discover the existence and location of objects in materials and to inspect metals and metal objects for flaws.
Basically, the ultrasonic transducer of an ultrasonic scanning system directs ultrasonic waves into a specimen and receives echoes generated when those waves strike acoustical interfaces within the specimen. Examples of an acoustical interface include the interface between a human organ and the surrounding tissue and the interface between metal and a flaw located therewithin. Generally, the echoes generated by the acoustical interfaces are converted to electrical signals by the transducer. Those signals are processed and displayed, usually on a cathode ray tube (CRT). By properly timing the generation of ultrasonic waves and the processing of returning echoes, the transducer can produce electrical signals that indicate acoustical interfaces exist within the specimen and that relate to the nature of those interfaces. By properly scanning the specimen and displaying on the CRT the electrical signals produced by the transducer, the examiner can actually see an image of the specimen, including acoustical interfaces located therein, under examination. Acoustical interfaces--such as those surrounding human organs, abnormalities in human organs, and flaws in metal pieces--can be readily viewed on a CRT by the examiner. An example of such an ultrasonic scanning transducer and system can be found in U.S. Pat. No. 4,092,867 issued to applicant herein.
Several factors determine the desirability of an ultrasonic transducer. The first factor is the resolution of the scanning system. If the resolution is not adequate, the examiner cannot determine the significance of the image displayed on the CRT. The second factor is the number of grey levels available in the display. The third factor is the ease with which the system can be used. The size and unwieldiness of the transducer itself determine in part the ease of use of the entire scanning system. The fourth factor is the cost of the transducer.